Hysterisis problem in faux â€œsplitsâ€ on Bud Pro~I

Mark McCornack · From: California, USA

A while ago, I lashed up my old Sho-Bud Pro~I to do splits on strings 5 & 10. No pedal/lever = B, A pedal = C#, pedal&knee = C, knee only = Bb. Pretty normal split application for E9. This is accomplished on the single-raise, single-lower changer with two-hole bellcranks and barrels. The raise rod goes through both the pedal bellcrank as well as the knee leverâ€™s bellcrank. The lower rod goes to knee lever Only. Those that have done this know what Iâ€™m talking about.

Anyway, this works pretty OK provided that I engage the pedal first and then engage the knee (to get the split C note). If i engage knee ahead of the A pedal, the C note is way out of tune.
So, there is a hysterisis issue, it appears, and I have no idea how to remedy this, or even if it can be remedied.

Has anybody out there done this â€œfaux splitâ€ with a single-raise / single-lower changer like this and encountered this hysterisis problem? Better yet, anybody encountered this and then come up with a fix. Confused

Dan Beller-McKenna · From: Durham, New Hampshire, USA

To directly answer your two closing questions: no. But, my old 6139 did develop a hysterisis problem on the eighth string, which was solved by reducing the number of wraps around the tuning shaft (and confirming that the roller nut was moving freely). Not sure whether that will help in this situation (a split), but could be worth a try. I was lead to the fewer-wrap solution through one or more Forum posts on the subject.

Good luck!

Jon Light · From: Saugerties, NY

Mark -- what you describe is, in my experience, common to other more modern raise/lower systems as well. It existed on my Carter, Fessenden and Williams.
I am not sure that hysteresis properly defines it. I've got an idea of what is happening physically but understanding it doesn't help much. I am resigned to studying my physical actions on the change, figuring which action, the raise or the lower, I am most likely to consistently do first, and tuning the change accordingly.

I believe that when the split is aided by hardware as in most modern guitars, either with a third rod or a lower-limiting screw, the discrepancy between raise first and lower first is greatly reduced. But not eliminated.

Ricky Davis · From: Bertram, Texas USA

(I just wrote that below; but now thinking about the way you are tuning?? So on the 5th string with a barrel behind "now" 3 raise rollers: the knee lower; the C pedal and A pedal. And a rod through the lower knee lever roller to the lower section of finger?? Ok Tune your open B note; then tune A pedal raise; then let off and then tune C pedal Raise; then let off. Now engage your A pedal and then lower the lever halftone to C and tune that one the lower rod. Then let pedal and knee off and make sure you have your normal B note...then engage lower and tune the half tone lower on the RAISE barrel; that barrel will BARELY engage...so it is so easy to accidentally have another raise barrel turn...is what I think might be happening also maybe.) and if all that tunes fine and you still are having a bad C note; try the stuff below)>>>
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Yes; take the "raise spring" off the finger...that is the spring that hooks to that bracket on bottom of guitar. Then retune everything and see if that helps. If not; try to make the raise section even lazier..but loosening the lower return spring to where the lower section BARELY returns from lowering; Then retune again. If that doesn't work; make sure you are using a .018p for the 5th string and .038w for 10th string.
Ricky
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Ricky Davis
Email Ricky: sshawaiian2362@gmail.com

Mark McCornack · From: California, USA

Thanks Ricky, Iâ€™ll fool around with that helper spring.
Just for clarification, I use the tuning procedure that you outlined here, and all the notes can indeed be achieved (Bb, B, C, C#) and tuned fine, but the â€œsplitâ€ C note is only in tune if I press the A lever (to raise full step) ahead of the lever (to lower a half step). If I lower the string to Bb with the knee, then try and raise it up to a C, the resultant note is horribly flat of C. If I release lever and pedal, then press the A pedal, then operate the knee lever, then weâ€™re back to a good in tune C note.
So, that my problem. Itâ€™s the order of pedal/knee actuation. For example, I could never have a Bb (knee engaged) and gliss up to a C note with the A pedal. It would never make it to a C. Rolling Eyes

Jon Light · From: Saugerties, NY

It is my assumption, with no basis other than .... making this up .... that just as we see when replacing a string with a heavier gauge that it will be cranked to more tension to come up to pitch and hence will require less changer movement to change pitch;

-- when a string is lowered, its tension is reduced and it requires more movement to be raised.
-- when that string is first raised, increasing the tension, it requires less movement to then lower it.

So the sequence of raise/lower vs. lower/raise is looking at two different scenarios as it they were two different string gauges/tensions.

Is that simplistic? Possibly. I totally made it up and I have zero schooling in any subject remotely relevant. But it rings true to me. As such, I assume that there is an optimal gauge whose tension-center (at rest) is the best compromise. My guess is that there is a gauge that would provide the least amount of differential between the sequences but I don't expect to see an elimination of the issue. I have never eliminated it.

I'll be most happy to learn that "no, that's not how it works, Jon", with a little bit of schooling on how it does work.

Mark McCornack · From: California, USA

Hi Jon. I did a little experiment here that shows that the issue is not intrinsic hysterisis in the string itself, but rather in the changer mechanism. I came up with a method to accurately measure the actual displacement of the string at the bridge (or very close).

I put a clamp on the string right there near the bridge, then measured movement relative the the body of the bridge. The black arm that is holding the gauge is firmly clamped to the body of the bridge. The plunger on the gauge is measuring the position of the C-clamp. The wooden block just translates this motion, as there was no way I could affix the gauge such that the plunger could directly contact the C-clamp. Here are the displacements I measured.

No pedal & no lever 0.0000 (datum)
Pedal A only = 0.0261
Knee lever only = -0.0108
Pedal A THEN knee lever = 0.0130
Knee lever THEN pedal = 0.0075

The key here is in the last two measurements. 13 mils versus 7.5 mils. This indicates that the culprit is in the changer. Maybe some weird balancing act with helper springs and lower return springs?

Below are pictures of my lashup....

Clamp on string.

Test setup with gauge and block translating clamp position to gauge

Mark McCornack · From: California, USA

Ricky...I tried your idea too. No change in measurements after removing raise helper and backing the return spring out a bit.
Iâ€™m so confused Rolling Eyes

Ricky Davis · From: Bertram, Texas USA

Yeah Mark; other than trying now the opposite of what I said about balancing the spring tension(Tighten lower return spring as far as you can stand the tension on the lowering it a half tone. And put raise spring back in)..then retune everything and try that. Also are you tuning your B to 440 or 440.5 or 441 open? and where is your C# note on the meter that you like?? and where do you like on the meter your Bb note to go and where do you hear the C note on the meter to be intune with what you are wanting??
Some how , some reason, like you were saying; is the changer seems to act differently between the raising and lowering when one is actuated and/or the other??? yes; so weird.....
I did use B lower a half a long time ago....but I eventually figured out how to get that move without the knee to do it... 7 different ways with different positions and other knee levers with other strings in the chording or movement.
Ricky
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Ricky Davis
Email Ricky: sshawaiian2362@gmail.com

Mark McCornack · From: California, USA

Thanks Ricky. Iâ€™ll give it a shot.
Even though this measurement setup I have looks a little Rube Goldburg-ish, Itâ€™s remarkably repeatable and accurate.
The difference between 13 mils (pedal then knee) versus 7.5 mils (knee then pedal) travel is close to a two-to-one, and the resultant C notes are off by multiple tens of cents from one another. So much so that the 440 vs 440.5 question is moot by comparison. The temperament Iâ€™m using is the one JD Maness did for the Peterson tuner. Nothing too odd.
I still much appreciate your showing me this trick with the old Bud changer to get the split. Even if I have to always pedal then knee to get the note, itâ€™s still worth having this split technique you showed me than not having it at all. I just wish it was insensitive to the pedal/knee order. This gives me a good puzzle to work on and itâ€™s good to keep the mind active in my advancing age Smile

Mark

Ricky Davis · From: Bertram, Texas USA

ok Brother....good luck.
Ricky
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Ricky Davis
Email Ricky: sshawaiian2362@gmail.com

Jon Light · From: Saugerties, NY

Mark -- I very possibly am misunderstanding your setup and test. It seems to me that you are still measuring the action of the string. Are not the forces being exerted upon it being spread out along the entire length, regardless of what point you pick out to observe and measure? It seems to me that your results are not inconsistent with my hypothesis. The test that I would want to see (that I have no ideas how to rig) is a measurement of the amount of movement in the rigid, non-elastic parts of the puzzle -- the bridge itself. How would you even start to rig up the measurement of this rotation movement? It would still need to be strung to provide the pounds of stress that the string's tension adds. Beats me.

Emphatically, this is not me being stubborn, digging in on an idea because it is MY idea......I just have a picture of what's going on that remains plausible to me. I would let go of in an instant, should I come to see that it simply is wrong.

Jerry Jones · From: Franklin, Tenn.

I suppose on an older Bud, the changer finger could be wallowed out from years of use and maybe causing the finger to resolve at two slightly different positions. Try shooting a little lub on that finger at the axle and see if your measurement changes.
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Jerry Jones

richard burton · From: Britain

I would look to see if the knee lever cross-shaft and the 'A' pedal cross-shaft are flexing, as this can cause the inconsistency that you are experiencing.

Try to eliminate any flex in the cross-shafts by installing some sort of center brace that the cross-shaft can 'kick against' during activation.

I put some center braces on my Marlen (red arrow)

Earnest Bovine · From: Los Angeles CA USA

I think all kinds of guitars do this to some extent. And I think it is not a problem because you can exploit it to get sweeter tempered chords. For example:
If you play an A minor chord, approach the C note from above so it comes out a few cents higher.
If you play a G# major chord, approach the B# note from below so it comes out a few cents lower.

Mark McCornack · From: California, USA

Thanks Doug. Unfortunately, this error is out of the realm of nuance. Rather than a discrepancy of a few cents, this sucker is off by â€œHalf a Buckâ€. The resultant tempered chord has distemper, and intervention must be made!

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